Nanobubbles Do Not Sit Alone at the Solid–Liquid Interface

Peng, Hong; Hampton, Marc A.; Nguyen, Anh V.

doi:10.1021/la305138v

Cited by 88 publications

(91 citation statements)

References 49 publications

(91 reference statements)

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“…NATURE COMMUNICATIONS | DOI: 10.1038/ncomms7068 ARTICLE dense gas layer) is the key stabilization mechanism 27,28 . The nanobubbles observed here can be stabilized by the mechanism described by the balance between diffusion and attraction of gas molecules to the graphene surface 26 .…”

Section: Resultsmentioning

confidence: 99%

Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells

et al. 2015

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Formation, evolution and vanishing of bubbles are common phenomena in nature, which can be easily observed in boiling or falling water, carbonated drinks, gas-forming electrochemical reactions and so on. However, the morphology and the growth dynamics of the bubbles at nanoscale have not been fully investigated owing to the lack of proper imaging tools that can visualize nanoscale objects in the liquid phase. Here, we demonstrate for the first time that the nanobubbles in water encapsulated by graphene membrane can be visualized by in-situ ultra-high vacuum transmission electron microscopy. Our microscopic results indicate two distinct growth mechanisms of merging nanobubbles and the existence of a critical radius of nanobubbles that determines the unusually long stability of nanobubbles. Interestingly, the gas transport through ultrathin water membranes at nanobubble interface is free from dissolution, which is clearly different from conventional gas transport that includes condensation, transmission and evaporation.

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Section: Resultsmentioning

confidence: 99%

Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells

et al. 2015

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“…26,39 Although experiments showed no gaseous layer in the absence of nanobubbles, 35 in the presence of nanobubbles experiments provided evidence of an interfacial gas layer. [40][41][42] It remains a question why the gas layer is only present when nanobubbles are present, and why it does not affect the macroscopic contact angle. 30 From a theoretical point of view, molecular dynamics simulations 26,43,44 showed reduced density near the hydrophobic surface in water due to accumulation of dissolved gas.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of Surface Nanobubbles

Zargarzadeh

Elliott

2016

Langmuir

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In this paper, we examine the thermodynamic stability of surface nanobubbles. The appropriate free energy is defined for the system of nanobubbles on a solid surface submerged in a supersaturated liquid solution at constant pressure and temperature, under conditions where an individual nanobubble is not in diffusive contact with a gas phase outside of the system or with other nanobubbles on the time scale of the experiment. The conditions under which plots of free energy versus the radius of curvature of the nanobubbles show a global minimum, which denotes the stable equilibrium state, are explored. Our investigation shows that supersaturation and an anomalously high contact angle (measured through the liquid) are required to have stable surface nanobubbles. In addition, the anomalously high contact angle of surface nanobubbles is discussed from the standpoint of a framework recently proposed by Koch, Amirfazli, and Elliott that relates advancing and receding contact angles to thermodynamic equilibrium contact angles, combined with the existence of a gas enrichment layer.

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“…Recently, Peng et al 23 used the AFM force mapping technique and measured long-range attraction forces (non-DLVO forces) between an AFM tip and nannobubbles at the interface between water and highly ordered pyrolytic graphite (HOPG). One characteristic of the AFM characterization is the jump-in distance, i.e., where strong attraction force appears.…”

Section: Introductionmentioning

confidence: 99%

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

2013

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Interfacial gas enrichment (IGE) covering the entire area of hydrophobic solid-water interface has recently been detected by atomic force microscopy (AFM) and hypothesized to be responsible for the unexpected stability and anomalous contact angle of gaseous nanobubbles, and the significant change from DLVO to non-DLVO forces. In this paper, we provide further proof of the existence of IGE in the form of a dense gas layer (DGL) by molecular dynamic simulation.Nitrogen gas adsorption at the water-graphite interface is investigated using molecular dynamic simulation at 300 K and 1 atm normal pressure. The results show that a DGL with a density equivalent to a gas at pressure of 500 atm is formed and equilibrated with a normal pressure of 1 atm. By varying the number of gas molecules in the system, we observe several types of dense gas domains: aggregates, cylindrical cap gas domains and DGLs. Spherical cap gas domains form during the simulation but are unstable and always revert to another type of the gas domains.Furthermore, the calculated surface potential of the DGL-water interface, -17.5 mV, is significantly closer to 0 than the surface potential, -65 mV, of normal gas bubble-water interface. This result supports our previously stated hypothesis that the change in surface potential causes the switch from repulsion to attraction for an AFM tip when the graphite surface is covered by an IGE layer. The change in surface potential comes from the structure change of water molecules at the DGL-water interface as compared with the normal gas-water interface. In addition, the contact angle of the cylindrical cap high density nitrogen gas domains is 141degrees. This contact angle is far greater 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 than 85 degrees observed for water on graphite at ambient conditions and much closer to the 150 degrees contact angle observed for nanobubbles in experiments.

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Nanobubbles Do Not Sit Alone at the Solid–Liquid Interface

Cited by 88 publications

References 49 publications

Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells

Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells

Thermodynamics of Surface Nanobubbles

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

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